Safety Study of XT-150 in Participants With ALS

Key Inclusion Criteria: * Adults between 18 and 80 years of age * Male or female, if of childbearing potential or sexually active, strict contraception required * Have ALS diagnosed by a doctor (specifically, sporadic or familial ALS diagnosed as clinically probable, lab-supported probable or definite ALS defined by the El Escorial criteria) * Have had symptoms of ALS (muscle weakness) within 36 months of starting this study * Have the ability to slowly exhale a volume of air at least 60% of what is expected for the participant's sex, height and age * Have not received treatment for ALS or are currently on a stable dose of an approved treatment for ALS. Patients currently receiving Tofersen are not eligible. * Able to receive the study injection intrathecally, determined by the study doctor * Able to undergo the study procedures and adhere to the study visit schedule at the time of study entry, with an estimated life expectancy of 6 months or greater Key Exclusion Criteria: * Have an implanted shunt to drain cerebrospinal fluid (CSF) or an implanted CNS catheter * Have an implanted of diaphragm pacing system * Tracheostomy * History or current diagnosis of cardiac conditions or ECG abnormalities indicating significant risk of safety for participants in the study * History or current diagnosis of respiratory conditions such as COPD * History or current diagnosis of cancer, chemical meningitis, HIV, Hep B, Hep C, uncontrolled diabetes * Presence of an autoimmune condition (f…